Runs the action, with the HTTP arguments as its arguments. That is, it's not looking for Jifty-encoded (J:F) arguments. If you have an action called "MyApp::Action::Ping" that takes a parameter, ip, this action will look for an HTTP argument called ip, (not J:F-myaction-ip).

Returns the action's result.

TODO, doc the format of the result.

On an invalid action name, throws a 404. On a disallowed action mame, throws a 403. On an internal error, throws a 500.